[v-erne]

I actually did not ask when you should use this but I guess this could just be normal engine off switch that is always used when on ground (just you should never touch it mid air) or maybe something also usefull when when you have some fire-like situation going on. The whole not use when flying as far as I remember was because it can be really hard to get the engine to work again. And the look of the switch conveyed this message really well.